1. Field of the Invention
The present invention relates to an electronic zoom technique in an image capturing apparatus such as a digital still camera or video camcorder.
2. Description of the Related Art
Recently, a large number of digital still cameras and digital video cameras using solid-state image sensors such as a CCD and CMOS are under development. Such cameras read out all pixels on an image sensor when capturing a still image, while they thin out and read out horizontal/vertical pixels when capturing a moving image to be framed or recorded. In this way, they maintain a necessary number of pixels and a necessary frame rate.
Under the circumstance, deterioration in image quality caused by thinning out pixels is unavoidable. Deterioration in image quality becomes prominent when electronic zoom is used. Normally, as shown in FIG. 10, electronic zoom is performed by extracting image data corresponding to a desired range of the field angle from image data on the full screen, enlarging the extracted image data, and displaying/recording the enlarged image data on the full screen. The displayed/recorded image has poorer quality than the image before electronic zoom.
A method disclosed in Japanese Patent Laid Open No. 2001-045364 is proposed as an approach to suppress deterioration in image quality.
Unfortunately, in the Japanese Patent Laid-Open No. 2001-045364, the frame rate decreases as the thinning ratio is changed to suppress deterioration in image quality upon electronic zoom. This is inconsistent with an improvement in image quality. Also, since a driving mode is uniquely defined for each thinning ratio, the image quality changes every time the driving mode is switched. A user may feel uncomfortable.